1. Field of the Invention
The present invention relates to a welding deformation computing method, a welding deformation computing device, and a computer program product for reducing a computation time of welding deformation when compared with a case in which nonlinear analysis is carried out for a whole region by dividing a structure, which is an object to be welded, into a region for which nonlinear analysis is necessary and a region for which linear analysis is sufficient and partly carrying out nonlinear analysis.
2. Description of Related Art
When building a welded structure using metallic material, deformation resulting from local heat history (hereinafter referred to as welding deformation) inevitably appears in structural members. Such welding deformation causes dimension errors, shape errors and the like of products and is directly linked to degradation in quality of products. Welding deformation also causes gaps, dislocations and the like between structural members in a production process and is one of factors that lie in the way of robotization and automation.
Therefore, if a degree of welding deformation can be predicted quantitatively and accurately, reduction of rework processes, promotion of robotization and automation and the like in producing a welded structure can be sought, and thus predicting a degree of welding deformation accurately is one of important tasks in production of welded structures.
To predict a degree of welding deformation accurately, nonlinear analysis must be carried out and a finite element method (hereinafter referred to as FEM) is frequently used. Also, a linear finite element method is often used as an approximate method by which local deformation such as transverse contraction, angular deformation, and longitudinal contraction generated near a welded portion is assumed as a known amount and deformation generated by such local deformation is linearly superimposed.
However, a large amount of processing time is necessary for computation of nonlinear analysis if a method is used by which nonlinear analysis is carried out in reference to the above-described welded structure, which is the object to be welded. In addition, if a deducing method of welding deformation using the linear finite element method is applied, there has been a problem that deducing accuracy may vary depending on how long a welded length is and it is difficult to maintain a certain level of deducing accuracy.
Though it is possible to compute welding deformation with high precision when nonlinear analysis using FEM is carried out in all regions of a welded structure, the degree n (n is a natural number) of simultaneous equations to be solved becomes larger and a computation time is proportional to n3.
Also, when nonlinear analysis is carried out, a whole welding process is divided by a short time interval into ms (ms is a natural number) steps and convergence computation is repeated mi (mi is a natural number) times sequentially in each step. Therefore, since the computation time increases in proportion to the following equation (1), the amount of consumption of computer resources becomes huge. When computing welding deformation of a large welded structure, for example, a result is actually computed only after a lapse of three days to one week.n3×ms×mi  (1)